PARATHYROID SCAN

This uses Tc-MIBI. So, it's not surprising that you see uptake in the heart and liver.
However, MIBI also goes to the thyroid and parathyroid.

The ability of the scan to diagnose parathyroid adenomas rests on the fact that these are rich in mitochondria.

So, after 1.5 hours of imaging, any spots that are still hot are going to be mitochondria-rich tissues. This could be a parathyroid adenoma, a carcinoma or for that matter a thyroid adenoma or carcinoma.

This is why the next step is to take a SPECT and see whether the hot point is lying where the thyroid lies or where the parathyroid lies.